The present invention relates to contact type magnetic disc apparatuses and, more particularly, to contact type magnetic disc apparatuses, in which a magnetic head is driven on frictional contact with a magnetic disc medium for recording and reproduction.
Recently, in data storage file fields, the recording density is being steadily improved. For increasing the recording density of the magnetic disc apparatus, it is thus one of the most important factors to reduce the gap between a magnetic head for writing and reading data and a magnetic disc medium storing the data. For reducing the gap between the magnetic head and the magnetic disc medium, a so-called contact type magnetic disc apparatus, in which the magnetic head is driven in frictional contact with the magnetic disc medium surface for recording and reproduction, has been developed (See, for instance H. Hamilton, Journal of Magnetic Society of Japan, Vol. 15, Supplement No. S2 (1991) 483, and also JapanesePatent Application No. 5-508808 (Japanese Patent Publication Disclosure No. 5-814495). In such contact type magnetic disc apparatuses, it is important to prevent wear and damages of the magnetic disc medium and the magnetic head.
Various techniques have been developed for the purpose of reducing the wear and damages in the contact type magnetic disc apparatus. For instance, Japanese Patent Laid-Open No. 2-249177 discloses a technique for preventing the wear of the magnetic disc medium and the magnetic head in such a manner that surplus liquid lubricant is always supplied to the magnetic disc medium surface by circulating the lubricant in the magnetic disc apparatus. Also, Japanese Patent Laid-Open No. 4-113568 discloses a technique, in which non-newton liquid lubricant is provided between the magnetic head and the magnetic disc medium in the same structure as above. Furthermore, Japanese Patent Laid-Open No. 5-1511735 discloses a slider structure which is suited for sliding over lubricant on the magnetic disc medium surface.
In the meantime, recent high recording density magnetic disc apparatuses mostly employ a separate recording and recording element type magnetic head, which uses an MR reproducing element utilizing magnetoresitive (MR) effect for reproducing data (hereinunder referred to as MR head). The MR head usually has a protective layer formed on the slider surface for the purposes of preventing the electric discharge of the element and improving the corrosion resistance thereof, as disclosed in, for instance, Japanese Patent Disclosure No. 4-364217. The wear of the protective layer of the head leads to deterioration of the MR head characteristics, and in the magnetic disc apparatus employing the MR element it is thus particularly important to suppress wear and damages of the head side protective layer. To this end, Japanese Patent Laid-Open No. 9-204626 discloses a magnetic disc apparatus having a protective layer on the sliding surface of the magnetic head, in which the hardness of the protective layer is set to be higher than two times, preferably three times, the hardness of a protective layer of the magnetic disc medium for preventing wear and damages of both the magnetic disc medium protective layer and the magnetic head protective layer.
The prior art magnetic disc apparatuses as shown above, however, have the following problems.
The magnetic disc apparatuses using liquid lubricant, as disclosed in the Japanese Patent Laid-Open No. 2-249177, 4-113568 and 5-151735, it is sought to suppress wear by always supplying surplus lubricant to the frictional surfaces of the magnetic head and the magnetic disc medium. However, the actual magnetic disc apparatus has a problem that it is extremely difficult to steadily supply clean lubricant at a constant rate so that it is difficult to ensure stable operation of the apparatus for long time.
The technique of providing protective layers on the sliding surface of the magnetic head and providing a protective layer on the magnetic disc medium as disclosed in the Japanese Patent Disclosure No. 9-204626, is effective so long as the magnetic disc medium protective layer has as large thickness as 15 nm or above. However, where the thickness of the protective layer is reduced to 10 nm or below, the magnetic disc medium protective layer may be worn and damaged, resulting in wear of the magnetic head protective layer. Particularly, since it is nowadays important to reduce the magnetic spacing to cope with a recent increasing recording density trend, it is important to reduce the thickness of the protective layer and layer.
In view of the above prior art, an object of the present invention concerns a magnetic disc medium, which permits recording and reproduction in a state that it can be in intermittent or continuous contact with a magnetic head, and it is sought to prevent wear and damages of a magnetic head protective layer and a magnetic disc protective layer in contact with each other, particularly it is sought to provide a magnetic disc apparatus, which is less subject to wear or damages even when the thicknesses of the magnetic head protective layer and the magnetic disc medium protective layer are reduced, as well as having high recording density and being excellently reliable.
According to an aspect of the present invention, there is provided a magnetic disc apparatus comprising a magnetic disc medium having a protective layer on the surface, a means for rotating the magnetic disc medium, a magnetic head for recording and reproducing data on and from the magnetic disc medium, and a control means for controlling the magnetic disc medium, the rotating means and the head, the head being rotated intermittently or continuously in frictional contact with the magnetic disc medium, wherein the head has a protective layer formed on at least part of a portion to be in frictional contact with the magnetic disc medium, the magnetic head protective layer having a density higher than the density of the magnetic disc medium protective layer.
With these settings, wear and damages due to the sliding are not caused partially on either the magnetic disc medium protective layer side or the magnetic head protective layer side, but they can proceed uniformly on both sides. Consequently, the degree of wear and damages can be extremely reduced. It is thus possible to provide a highly reliable magnetic disc apparatus, which is subject to less wear and damages and excellently reliable.
According to another aspect of the present invention, there is provided a magnetic disc apparatus comprising a magnetic disc medium having a protective layer on the surface, a means for rotating the magnetic disc medium, a magnetic head for recording and reproducing data on and from the magnetic disc medium, and a control means for controlling the magnetic disc medium, the rotating means and the head, the head being rotated intermittently or continuously in frictional contact with the magnetic disc medium, wherein the magnetic head protective layer has a Young""s modulus higher than the Young""s modulus of the magnetic disc medium protective layer.
According to other aspect of the present invention, there is provided a magnetic disc apparatus comprising a magnetic disc medium having a protective layer of thickness between 1 and 10 nm on the surface, a means for rotating the magnetic disc medium, a magnetic head for recording and reproducing data on and from the magnetic disc medium, and a control means for controlling the magnetic disc medium, the rotating means and the head, wherein the head has a protective layer formed on at least part of a portion to be in frictional contact with the magnetic disc medium, the magnetic head protective layer of a hardness between 1.5 and 2.0 times the hardness of the magnetic disc medium protective layer.
The magnetic head protective layer and the magnetic disc medium protective layer are made of the same material. The magnetic head protective layer and the magnetic disc medium protective layer are made of material including mainly carbon.
According to still other aspect of the present invention, there is provided a magnetic disc apparatus comprising a magnetic disc medium having a protective layer on its surface, and a magnetic head for recording and reproducing data on and from the magnetic disc medium having a protective layer on its surface, the magnetic disc medium and the magnetic head being rotated in frictional contact therebetween, wherein the magnetic head protective layer having a density higher than the density of the magnetic disc medium protective layer.
According to further aspect of the present invention, there is provided a magnetic disc apparatus comprising a magnetic disc medium having a protective layer on its surface, and a magnetic head for recording and reproducing data on and from the magnetic disc medium having a protective layer on its surface, the magnetic disc medium and the magnetic head being rotated in frictional contact therebetween, wherein the magnetic head protective layer has a Young""s modulus higher than the Young""s modulus of the magnetic disc medium protective layer.
According to still further aspect of the present invention, there is provided a magnetic disc apparatus comprising a magnetic disc medium having a protective layer on its surface, and a magnetic head for recording and reproducing data on and from the magnetic disc medium having a protective layer on its surface, the magnetic disc medium and the magnetic head being rotated in frictional contact therebetween, wherein the magnetic head protective layer of a hardness between 1.5 and 2.0 times the hardness of the magnetic disc medium protective layer
The densities of the magnetic disc medium protective layer and the magnetic head protective layer are set to be in ranges of 1.2 to 1.8 (g/cm3) and 1.0 to 2.0 (g/cm3), respectively. The Young""s moduluses of the magnetic disc medium protective layer and the magnetic head protective layer are set to be in ranges of 200 to 400 (GPa) and 150 to 500 (GPa), respectively. The thickness of the magnetic disc medium protective layer is set to be between 1 and 10 nm, and the hardness of the magnetic head protective layer is set to be between 1.5 and 2.0 times the hardness of the magnetic disc medium protective layer. The thickness of the magnetic disc medium protective layer is 15 nm or above, and the hardness of the magnetic head protective layer is higher than 2.0 times the hardness of the magnetic disc medium protective layer. The magnetic head protective layer and the magnetic disc medium protective layer are formed as a carbon layer with or without a hydrogen or nitrogen content. The magnetic head protective layer and the magnetic disc medium protective layer are formed as SiC, SiN or BN.
Other objects and features will be clarified from the following description with reference to attached drawings.